Republican presidential candidate Marco Rubio on Tuesday called for an overhaul of the U.S. higher education system, saying colleges were operating as a "cartel" and were not meeting the needs of students or the economy.

"We do not need timid tweaks to the old system. We need a holistic overhaul," Rubio said in a policy speech in Chicago. "We need to change how we provide degrees, how those degrees are accessed, how much that access costs, how those costs are paid, and even how those payments are determined."

The speech was part of a move by the U.S. senator from Florida to raise his visibility on the campaign trail after focusing on Senate business over the past several weeks. Rubio is in a crowded field of 14 declared candidates vying to represent the Republican Party in the November 2016 election.

It also was an opportunity for Rubio to expound on what has become the central theme of his candidacy: preparing America for a future that will be shaped by the forces of globalization, automation, and rapid technological change.

"We either adjust to it or embrace it, or we will be left behind by the future," he said in remarks after his speech at an incubator for technology start-ups.

As part of his campaign message, Rubio has sought to warn voters that the United States as it was before the economic downturn that began in 2007 will never return.

In his speech, he warned that the path to prosperity for the American middle class has narrowed not as a "result of a cyclical economic downturn that will naturally correct itself. It is born of a fundamental transformation to the very nature of our economy."

To that end, Rubio has embraced rhetoric that sometimes sounds atypical of conservative candidates: proposing a tax plan that seeks to boost the poor and working class and does not significantly slice top-tier tax rates; calling for subsidies to assist minimum-wage workers, and, as he emphasized on Tuesday, pushing for a new approach to higher education that is less grounded in traditional liberal-arts instruction and more in teaching high-level skills that will enable graduates to compete in a global business environment.

"We still tell students that to get a degree, they have to spend four years on a campus; tens of thousands of dollars on tuition, books, room, board; and hundreds of hours in a classroom, often learning subjects that aren't relevant to the modern economy," Rubio said.

"The result is that many young people are graduating with mountains of debt for degrees that will not lead to jobs, and many who need higher education the most – such as single parents and working adults – are left with few options that fit their schedules and budgets."

To break up what he called the higher-education "cartel," Rubio pledged to create a new accreditation process that would allow low-cost providers — perhaps largely online - to compete with established schools. He has called for colleges to tell potential students how much salary they can expect to earn for a given degree before they commit themselves to a major.

Rubio, who was saddled with student loans himself as a college graduate, wants students to be allowed to repay loans based on their postgraduate incomes. He has also proposed a plan that would allow investors to pay a student's tuition in return for a percentage of the student's income after graduation.

After the speech, Rubio left for Iowa, where he planned to spend three days trying to get into the mix in that early voting state. Social conservatives such as Wisconsin Governor Scott Walker, who is expected to announce his candidacy next week, populist candidate Ben Carson, and Senator Rand Paul of Kentucky have appeared to hold an early advantage in Iowa.

2. Attended Tarkio College for one year on a football scholarship before he later transferred to Santa Fe College.

(REUTERS/Chris Keane)

3. When he was sworn into office in 2011, he said that he owed $100,000 of student loans which he finally paid off in 2012.

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4. His wife of 17 years, Jeanette, is of Colombian descent and was once a Miami Dolphins cheerleader.

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5. He went viral with a sip of water. Rubio gave the official Republican reaction to the State of the Union in 2013, but the only detail most people remembered was the moment in which he became so parched that he reached for a water bottle to quench his thirst.

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6. Though he was baptized as an infant in the Catholic church, he was also baptized as Mormon later in childhood when his family lived in Las Vegas. He is now a practicing Catholic.

(Photo By Tom Williams/CQ Roll Call)

7. He teaches political science at Florida International University in Miami.

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8. He says the first concert he ever attended was a Prince show.

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9. His family used to call him Tony, which came from his middle name Antonio.